1Tie::Scalar(3pm)       Perl Programmers Reference Guide       Tie::Scalar(3pm)
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NAME

6       Tie::Scalar, Tie::StdScalar - base class definitions for tied scalars
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SYNOPSIS

9           package NewScalar;
10           require Tie::Scalar;
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12           @ISA = qw(Tie::Scalar);
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14           sub FETCH { ... }           # Provide a needed method
15           sub TIESCALAR { ... }       # Overrides inherited method
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18           package NewStdScalar;
19           require Tie::Scalar;
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21           @ISA = qw(Tie::StdScalar);
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23           # All methods provided by default, so define only what needs be overridden
24           sub FETCH { ... }
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27           package main;
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29           tie $new_scalar, 'NewScalar';
30           tie $new_std_scalar, 'NewStdScalar';
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DESCRIPTION

33       This module provides some skeletal methods for scalar-tying classes.
34       See perltie for a list of the functions required in tying a scalar to a
35       package. The basic Tie::Scalar package provides a "new" method, as well
36       as methods "TIESCALAR", "FETCH" and "STORE". The Tie::StdScalar package
37       provides all the methods specified in  perltie. It inherits from
38       Tie::Scalar and causes scalars tied to it to behave exactly like the
39       built-in scalars, allowing for selective overloading of methods. The
40       "new" method is provided as a means of grandfathering, for classes that
41       forget to provide their own "TIESCALAR" method.
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43       For developers wishing to write their own tied-scalar classes, the
44       methods are summarized below. The perltie section not only documents
45       these, but has sample code as well:
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47       TIESCALAR classname, LIST
48           The method invoked by the command "tie $scalar, classname".
49           Associates a new scalar instance with the specified class. "LIST"
50           would represent additional arguments (along the lines of
51           AnyDBM_File and compatriots) needed to complete the association.
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53       FETCH this
54           Retrieve the value of the tied scalar referenced by this.
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56       STORE this, value
57           Store data value in the tied scalar referenced by this.
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59       DESTROY this
60           Free the storage associated with the tied scalar referenced by
61           this.  This is rarely needed, as Perl manages its memory quite
62           well. But the option exists, should a class wish to perform
63           specific actions upon the destruction of an instance.
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65   Tie::Scalar vs Tie::StdScalar
66       "Tie::Scalar" provides all the necessary methods, but one should
67       realize they do not do anything useful. Calling "Tie::Scalar::FETCH" or
68       "Tie::Scalar::STORE" results in a (trappable) croak. And if you inherit
69       from "Tie::Scalar", you must provide either a "new" or a "TIESCALAR"
70       method.
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72       If you are looking for a class that does everything for you you don't
73       define yourself, use the "Tie::StdScalar" class, not the "Tie::Scalar"
74       one.
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MORE INFORMATION

77       The perltie section uses a good example of tying scalars by associating
78       process IDs with priority.
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82perl v5.12.4                      2011-06-01                  Tie::Scalar(3pm)
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